Heretofore, there has been known in the prior art a plug-in fuse carrier which has been operable as a surge-current protector in connection with the cross-connection of two rows of terminals of a telephone terminal block, conventionally referred to as an AT&T Style 110 Block, which is commonly used within telephone and other electronic applications. Such a fuse carrier is illustrated and described within U.S. Pat. No. 4,968,264 which was issued to William E. Ruehl et al. and is assigned to the same assignee as that of the present patent application. The fuse carrier disclosed within this patent comprises an insulating housing 12, and a cover 14 which is mounted upon the housing. The cover 14 includes a first platform 16 disposed upon one end thereof, and a second platform 18 disposed upon the other end thereof. The cover 14 is disposed upon the housing 12 so as to enclose a cavity 20 which is therefore defined within the housing 12. Fuses 22 and 24, having a tubular configuration, are mounted within the cavity 20 in an off-set manner so as to accommodate their diametrical dimensions and to minimize the space requirements within the cavity 20. Each one of the fuses 22 and 24 includes contact blades 32, 36 extending through aligned slits defined within the housing end walls for resting against an upright 88 and for providing a contact area within a gap 86 defined within each end of the fuse carrier. The fuse carrier is readily insertable between the two rows of terminals of the terminal block so as to interconnect two circuits, operatively associated with the terminal block, by means of the fuses 22, 24.
Accordingly, it is seen that the aforenoted type of prior art fuse carrier only provided over-current or surge-current protection. However, it is also well-known that telephone circuits normally operate upon relatively low voltage levels but are sometimes exposed to transient voltages which are considerably greater than the normal operating voltages. Such transient voltages may be caused, for example, by means of a lightning strike, a short circuit connection with a high voltage line, and the like. Therefore, it is also desirable to provide high transient voltage or over-voltage protection for such telephone circuitry. While the prior art is additionally known to disclose plug-in structures which are able to be used in connection with telephone terminal blocks and which include various electrical components for protecting the telephone circuitry against high transient voltage or over-voltage conditions, there was a need in the art, to which the invention embodied and disclosed within the aforenoted parent, pending United States Patent application Ser. No. 07/923,249, now U.S. Pat. No. 5,341,269 was directed, for a device and structural arrangement which could readily and compactly provide both over-current and over-voltage protection for the terminal block circuitry.
Briefly, in accordance with the composite voltage protector and grounding bar arrangement for telephone terminal blocks as disclosed within the aforenoted parent, pending United States patent application Ser. No. 07/923,249, now U.S. Pat. No. 5,341,269, there was disclosed a two-piece interfitting housing having an over-voltage protection device disposed therein and operatively connected to a ground contact. A strip-like grounding bar was configured so as to be able to be disposed within a longitudinally extending channel defined between two rows of laterally spaced terminals provided upon the telephone terminal block, the grounding bar being provided with a longitudinally extending array of holes into which the ground contact of the two-piece housing was able to be disposed. A plurality of terminal/fuse contacts were also provided internally within the two-piece housing, and plug-in surge-current or over-current protection means, such as, for example, a fuse carrier, was operatively mounted upon the housing for connection to the terminal/fuse contacts. The terminal/fuse contacts also interconnected opposed terminals of the two rows of laterally spaced terminals of the telephone terminal block.
While the foregoing composite voltage protector and grounding bar arrangement has in fact provided the necessary voltage and current protection requirements, it has been alternatively realized or desired that in conjunction with particular or specific telephone terminal blocks, arrangements, or applications, such a composite voltage protector and grounding bar arrangement is not in fact required. For example, in connection with a particular or specific telephone terminal block, arrangement, or application, over-current protection may already be effectively provided or incorporated within the system or circuitry by means of a suitable over-current or surge-current device which is located externally of, or at a location remote from, the two-piece housing. Nevertheless, in order to simplify manufacture of the two-piece housings, and to further minimize manufacturing costs thereof, it is desired to provide similar or standardized housings regardless of whether or not the housings will accommodate an over-current or surge-current device. In such a situation, therefore, the same or similar housing may simply accommodate a bridging-clip device whereby this altered composite voltage protector and grounding bar arrangement only provides over-voltage or surge-voltage protection. Similarly, and yet still further, in conjunction with still other particular or specific telephone terminal blocks, arrangements, or applications, in lieu of providing over-current or surge-current protection in the form of fuse devices, it is sometimes desirable or required to provide such protection in the form of positive-temperature-coefficient (PTC) current-limiting devices which are automatically resettable. Again, it is desired to be able to provide or mount such devices upon the same or similar housing whereby the manufacture of such housings is able to be maintained uniform or standardized. Lastly, it is further desired in conjunction with other telephone terminal blocks, arrangements, and applications, to provide over-current or surge-current, or over-voltage or surge-voltage, protection with respect to both sides of the particular circuits being protected in order to protect the circuits from over-current or surge-current, or over-voltage or surge-voltage, conditions which may be generated in a multiplicity of directions, such as, for example, from the telephone central office, from the customer premises, or from the customer ground line. Consequently, in is likewise desired to be able to provide or mount such devices upon housings which are substantially or sufficiently similar to the aforenoted housing of the noted parent, pending United States patent application Ser. No. 07/923,249, now U.S. Pat. No. 5,341,269, whereby such newly configured, similar housings are nevertheless able to be used in conjunction with the same telephone terminal blocks, that is, for example, the AT&T Style 110 Block.